An apparatus for the measurement of current gain in the range 1 - 300 Mc/s

An apparatus has been constructed for measuring the modulus of the near-short-circuit current gain of transistors in the frequency range 1¿300 Mc/s. Both common-base and common-emitter measurements can be made. Measurements are made by injecting a current into the input lead of the transistor via a wide-band shielded transformer. Similar measuring impedances of 5¿10 ohms are connected in the input and output circuits and enable the currents flowing in these circuits to be measured. Special precautions were necessary in the design of the input transformer and the measuring resistors to obtain satisfactory operation over the operating frequency range, and the equipment takes the form of an L-shaped assembly having the transistor test sockets at the intersection of the two arms. The zero error introduced by the apparatus is less than 0.4dB over the operating range of frequencies, and the parasitic shunt capacitance within the instrument at the input connection is made less than 0.01 pF by the use of a guard-ring technique